colloquial term for an important or high-ranking person (a 'big shot' or 'higher-up')
会社の偉いさんに直談判するのは勇気がいる。
It takes courage to speak directly to the big shots in the company.
偉いさんが来ると、雰囲気がピリッとする。
When the higher-ups arrive, the atmosphere becomes tense.
あの人は偉いさんだから、言葉に気を付けたほうがいい。
That person is an important figure, so you should watch your words.